Method and system for seamless address allocation in a data-over-cable system

ABSTRACT

A method and system is provided to send and receive Dynamic Host Configuration Protocol (“DHCP”) messages in a data-over-cable system via a route with one or more routers. The routers may apply one or more different protocol filters to DHCP messages, such as filtering out DHCP messages with a “Martian” Internet Protocol (“IP”) address (e.g., 0.0.0.0) and other characteristics. The Martian IP address is commonly used as an initial IP address in a DHCP initialization sequence but is often filtered out by routers as an invalid IP address. DHCP messages are received by a first protocol agent from a first User Datagram Protocol (“UDP”) port. The first UDP port is used by DHCP servers and network devices such as cable modems and customer premise equipment to send and receive DHCP messages via a route that may apply one or more DCHP filters. The first protocol agent sends the DHCP messages to a second protocol agent on a second UDP port via a route that does not apply filters to the DHCP messages. The first protocol agent receives DHCP messages from the second protocol agent on the second UDP port. The first protocol agent sends messages back to a DHCP protocol server or network device such as a cable modem on the first UDP port. The protocol agent allows DHCP messaging to be seamlessly used in a data-over-cable system with routers that apply a variety of protocol filters to DHCP messages.

FIELD OF INVENTION

The present invention relates to communications in computer networks.More specifically, it relates to a method and system for protocolmessaging in a cable modem in a data-over-cable system.

BACKGROUND OF THE INVENTION

Cable television networks such as those provided by Comcast CableCommunications, Inc., of Philadelphia, Pa., Cox Communications ofAtlanta Ga., Tele-Communications, Inc., of Englewood, Colo., Time-WarnerCable, of Marietta, Ga., Continental Cablevision, Inc., of Boston,Mass., and others provide cable television services to a large number ofsubscribers over a large geographical area. The cable televisionnetworks typically are interconnected by cables such as coaxial cablesor a Hybrid Fiber/Coaxial (“HFC”) cable system which have data rates ofabout 10 Mega-bits-per-second (“Mbps”) to 30+ Mbps.

The Internet, a world-wide-network of interconnected computers, providesmulti-media content including audio, video, graphics and text thattypically require a large bandwidth for downloading and viewing. MostInternet Service Providers (“ISPs”) allow customers to connect to theInternet via a serial telephone line from a Public Switched TelephoneNetwork (“PSTN”) at data rates including 14,400 bps, 28,800 bps, 33,600bps, 56,000 bps and others that are much slower than the about 10 Mbpsto 30+ Mbps available on a coaxial cable or HFC cable system on a cabletelevision network.

With the explosive growth of the Internet, many customers have desiredto use the larger bandwidth of a cable television network to connect tothe Internet and other computer networks. Cable modems, such as thoseprovided by 3Com Corporation of Santa Clara, Calif., MotorolaCorporation of Arlington Heights, Ill., Hewlett-Packard Co. of PaloAlto, Calif., Bay Networks of Santa Clara, Calif., Scientific-Atlanta,of Norcross, Ga. and others offer customers higher-speed connectivity tothe Internet, an intranet, Local Area Networks (“LANs”) and othercomputer networks via cable television networks. These cable modemscurrently support a data connection to the Internet and other computernetworks via a cable television network with a data rate of up to 30+Mbps which is a much larger data rate than can be supported by a modemused over a serial telephone line.

However, most cable television networks provide only uni-directionalcable systems, supporting only a “downstream” data path. A downstreamdata path is the flow of data from a cable system “headend” to acustomer. A cable system headend is a central location in the cabletelevision network that is responsible for sending cable signals in thedownstream direction. A return data path via a telephone network, suchas a public switched telephone network provided by AT&T and others,(i.e., a “telephony return”) is typically used for an “upstream” datapath. An upstream data path is the flow of data from the customer backto the cable system headend. A cable television system with an upstreamconnection to a telephony network is called a “data-over-cable systemwith telephony return.”

An exemplary data-over-cable system with telephony return includescustomer premise equipment (e.g., a customer computer), a cable modem, acable modem termination system, a cable television network, a publicswitched telephone network, a telephony remote access concentrator and adata network (e.g., the Internet). The cable modem termination systemand the telephony remote access concentrator together are called a“telephony return termination system.”

The cable modem termination system receives data packets from the datanetwork and transmits them downstream via the cable television networkto a cable modem attached to the customer premise equipment. Thecustomer premise equipment sends response data packets to the cablemodem, which sends response data packets upstream via public switchedtelephone network to the telephony remote access concentrator, whichsends the response data packets back to the appropriate host on the datanetwork.

When a cable modem used in the data-over-cable system with telephonyreturn is initialized, a connection is made to both the cable modemtermination system via the cable network and to the telephony remoteaccess concentrator via the public switched telephone network. As acable modem is initialized, it will initialize one or more downstreamchannels (i.e., downstream connections) to the cable modem terminationsystem via the cable network or the telephony remote access concentratorvia the public switched telephone network.

As a cable modem is initialized in a data-over-cable system, itregisters with a cable modem termination system to allow the cable modemto receive data over a cable television connection and from a datanetwork (e.g., the Internet or an Intranet). The cable modem forwardsconfiguration information it receives in a configuration file duringinitialization to the cable modem termination system as part of aregistration request message.

Many data-over-cable systems in the prior art use a Dynamic HostConfiguration Protocol (“DHCP”) as a standard messaging protocol toallocate network addresses such as Internet Protocol (“IP”) addresses.As is known in the art, DHCP is a protocol for passing configurationinformation to network devices on a network. IP is an addressingprotocol designed to route traffic within a network or between networks.DHCP uses User Datagram Protocol (“UDP”) as a transport protocol. DHCPmessages sent from a network device to a DHCP server are sent via UDPDHCP server-port-67, and DHCP messages from a DHCP server to a networkdevice are sent via UDP DHCP client-port-68. DHCP messaging starts withthe use of a “Martian” IP address (e.g., 0.0.0.0) as a source addressfor a network device (e.g., a cable modem) since no legitimate IPaddress has been assigned to the network device.

Since a DHCP server may be at a different geographical location fromother network devices in the data-over-cable system, DHCP messages maypass through one or more routers on a network such as thedata-over-cable system. As is known in the art, routers route datapackets to an appropriate network device on a network based on a networkaddress.

Routers typically use one or more types of filters to provide varyinglevels of security to a network. For example, a first type of router mayfilter all inbound messages that do not have an IP address for aspecified network (e.g., an intranet). A second type of router mayfilter all outbound messages that are not addressed to a specific IPaddress. In a data-over-cable system, many routers have default filtersthat filter out all external DHCP messages regardless of the sourceaddress to prevent a rogue network device from being assigned alegitimate IP address on the data-over-cable system. In addition, manyrouters in a data-over-cable system filter DHCP messages with a Martiansource address since such a source address is often used to launch anattack on a data-over-cable system.

Thus, it is desirable to use DHCP messaging to allocate networkaddresses in a data-over-cable system with routers that may employ DHCPfilters. It is also desirable to use DHCP messaging with Martian sourceaddresses with routers that use filters to filter DHCP messages withMartian source addresses.

SUMMARY OF THE INVENTION

In accordance with a preferred embodiment of the present invention, theproblems associated with DHCP filters in routers in a data-over-cablesystem are overcome. A method and system for seamless network addressallocation is provided. The method includes receiving a first messagewith a first protocol from a first network device on a first port on aprotocol agent. The first port is used to send messages from the firstprotocol server via a route that may apply one or more protocol filtersto the first protocol. The first message is sent from the protocol agenton a second port. The second port is used to send messages with thefirst protocol via a route that does not apply protocol filters to thefirst protocol. A second message is received on the second port on theprotocol agent. The second message is sent from the protocol agent tothe first network device on the first port.

In a preferred embodiment of the present invention, the first protocolis DHCP, the first network device is any of a protocol server, cablemodem, or cable modem termination system and the first port is a UDPDHCP port (e.g., UDP DHCP port 67 or 68). The second port is a UDP portother than a UDP DHCP port (e.g., other than UDP DHCP port 67 or 68).However, the present invention is not limited to these network devices,protocols and ports, and other network devices, protocols and portscould also be used (e.g., BOOT Transmission Protocol (“BOOTP”) andTransmission Control Protocol (“TCP”) ports).

The system includes a protocol agent, for sending and receiving messagesfor a first protocol in a data-over-cable system. The system alsoincludes a protocol agent port for sending and receiving messages forthe first protocol in a data-over-cable system. The protocol agent portis used to send and receive messages via a route that does not applyprotocol filters to the first protocol in a data-over-cable system. In apreferred embodiment of the present invention, the protocol agent is aDHCP agent, and the protocol agent port is a UDP port other than a UDPDHCP port (e.g., other than UDP port 67 or 68). However, the presentinvention is not limited to these protocols and ports, and otherprotocols and ports could also be used.

The foregoing and other features and advantages of a preferredembodiment of the present invention will be more readily apparent fromthe following detailed description, which proceeds with references tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a cable modem system withtelephony return;

FIG. 2 is a block diagram illustrating a protocol stack for a cablemodem;

FIG. 3 is a block diagram illustrating a Telephony Channel Descriptormessage structure;

FIG. 4 is a block diagram illustrating a Termination System Informationmessage structure;

FIG. 5 is a flow diagram illustrating a method for addressing hosts in acable modem system;

FIG. 6 is a block diagram illustrating a Dynamic Host ConfigurationProtocol message structure;

FIGS. 7A and 7B are a flow diagram illustrating a method for discoveringhosts in a cable modem system;

FIG. 8 is a block diagram illustrating a data-over-cable system for themethod illustrated in FIGS. 7A and 7B;

FIG. 9 is a block diagram illustrating the message flow of the methodillustrated in FIGS. 7A and 7B;

FIGS. 10A and 10B are a flow diagram illustrating a method for resolvinghost addresses in a data-over-cable system;

FIG. 11 is a flow diagram illustrating a method for resolving discoveredhost addresses; and

FIG. 12 is a block diagram illustrating the message flow of the methodillustrated in FIG. 10;

FIGS. 13A and 13B are a flow diagram illustrating a method for obtainingaddresses for customer premise equipment;

FIGS. 14A and 14B are a flow diagram illustrating a method for resolvingaddresses for customer premise equipment;

FIGS. 15A and 15B are a flow diagram illustrating a method foraddressing network host interfaces from customer premise equipment;

FIGS. 16A and 16B are a flow diagram illustrating a method for resolvingnetwork host interfaces from customer premise equipment;

FIG. 17 is a block diagram illustrating a message flow for the methodsin FIGS. 15A, 15B, and 16A and 16B;

FIG. 18 is a block diagram illustrating a data-over-cable system withprotocol messaging;

FIG. 19 is a flow diagram illustrating a method for protocol messaging;

FIG. 20 is a flow diagram illustrating a method for protocol messaging;

FIG. 21 is a flow diagram illustrating a method for protocol messaging;and

FIG. 22 is a flow diagram illustrating a method for protocol messaging.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Cable Modem System With Telephony Return

FIG. 1 is a block diagram illustrating a data-over-cable system withtelephony return 10, hereinafter data-over-cable system 10. Most cableproviders known in the art predominately provide uni-directional cablesystems, supporting only a “downstream” data path. A downstream datapath is the flow of data from a cable television network “headend” tocustomer premise equipment (e.g., a customer's personal computer). Acable television network headend is a central location that isresponsible for sending cable signals in a downstream direction. Areturn path via a telephony network (“telephony return”) is typicallyused for an “upstream” data path in uni-directional cable systems. Anupstream data path is the flow of data from customer premise equipmentback to the cable television network headend.

However, data-over-cable system 10 of the present invention may alsoprovide a bi-directional data path (i.e., both downstream and upstream)without telephony return as is also illustrated in FIG. 1 and thepresent invention is not limited to a data-over-cable system withtelephony return. In a data-over cable system without telephony return,customer premise equipment or cable modem has an upstream connection tothe cable modem termination system via a cable television connection, awireless connection, a satellite connection, or a connection via othertechnologies to send data upstream to the cable modem terminationsystem.

Data-over-cable system 10 includes a Cable Modem Termination System(“CMTS”) 12 connected to a cable television network 14, hereinaftercable network 14. FIG. 1 illustrates one CMTS 12. However,data-over-cable system 10 can include multiple CMTS 12. Cable network 14includes cable television networks such as those provided by ComcastCable Communications, Inc., of Philadelphia, Pa., Cox Communications, orAtlanta, Ga., Tele-Communications, Inc., of Englewood, Colo.,Time-Warner Cable, of Marietta, Ga., Continental Cablevision, Inc., ofBoston, Mass., and others. Cable network 14 is connected to a CableModem (“CM”) 16 with a downstream cable connection. CM 16 is any cablemodem such as those provided by 3Com Corporation of Santa Clara, Calif.,Motorola Corporation of Arlington Heights, Ill., Hewlett-Packard Co. ofPalo Alto, Calif., Bay Networks of Santa Clara, Calif.,Scientific-Atlanta, of Norcross, Ga. and others. FIG. 1 illustrates oneCM 16. However, in a typical data-over-cable system, tens or hundreds ofthousands of CM 16 are connected to CMTS 12.

CM 16 is connected to Customer Premise Equipment (“CPE”) 18 such as apersonal computer system via a Cable Modem-to-CPE Interface (“CMCI”) 20.CM 16 is connected to a Public Switched Telephone Network (“PSTN”) 22with an upstream telephony connection. PSTN 22 includes those publicswitched telephone networks provided by AT&T, Regional Bell OperatingCompanies (e.g., Ameritch, U.S. West, Bell Atlantic, Southern BellCommunications, Bell South, NYNEX, and Pacific Telesis Group), GTE, andothers. The upstream telephony connection is any of a standard telephoneline connection, Integrated Services Digital Network (“ISDN”)connection, Asymmetric Digital Subscriber Line (“ADSL”) connection, orother telephony connection. PSTN 22 is connected to a Telephony RemoteAccess Concentrator (“TRAC”) 24. In a data-over cable system withouttelephony return, CM 16 has an upstream connection to CMTS 12 via acable television connection, a wireless connection, a satelliteconnection, or a connection via other technologies to send data upstreamoutside of the telephony return path. An upstream cable televisionconnection via cable network 14 is illustrated in FIG. 1.

FIG. 1 illustrates a telephony modem integral to CM 16. In anotherembodiment of the present invention, the telephony modem is a separatemodem unit external to CM 16 used specifically for connecting with PSTN22. A separate telephony modem includes a connection to CM 16 forexchanging data. CM 16 includes cable modems provided by the 3ComCorporation of Santa Clara, Calif., U.S. Robotics Corporation of Skokie,Ill., and others. In yet another embodiment of the present invention, CM16 includes functionality to connect only to cable network 14 andreceives downstream signals from cable network 14 and sends upstreamsignals to cable network 14 without telephony return. The presentinvention is not limited to cable modems used with telephony return.

CMTS 12 and TRAC 24 may be at a “headend” of cable system 10, or TRAC 24may be located elsewhere and have routing associations to CMTS 12. CMTS12 and TRAC 24 together are called a “Telephony Return TerminationSystem” (“TRTS”) 26. TRTS 26 is illustrated by a dashed box in FIG. 1.CMTS 12 and TRAC 24 make up TRTS 26 whether or not they are located atthe headend of cable network 14, and TRAC 24 may in located in adifferent geographic location from CMTS 12. Content severs, operationsservers, administrative servers and maintenance servers used indata-over-cable system 10 (not shown in FIG. 1) may also be in differentlocations. Access points to data-over-cable system 10 are connected toone or more CMTS's 12 or cable headend access points. Suchconfigurations may be “one-to-one”, “one-to-many,” or “many-to-many,”and may be interconnected to other Local Area Networks (“LANs”) or WideArea Networks (“WANs”).

TRAC 24 is connected to a data network 28 (e.g., the Internet or anintranet) by a TRAC-Network System Interface 30 (“TRAC-NSI”). CMTS 12 isconnected to data network 28 by a CMTS-Network System Interface(“CMTS-NSI”) 32. The present invention is not limited to data-over-cablesystem 10 illustrated in FIG. 1, and more or fewer components,connections and interfaces could also be used.

Cable Modem Protocol Stack

FIG. 2 is a block diagram illustrating a protocol stack 36 for CM 16.FIG. 2 illustrates the downstream and upstream protocols used in CM 16.As is known in the art, the Open System Interconnection (“OSI”) model isused to describe computer networks. The OSI model consists of sevenlayers including from lowest-to-highest, a physical, data-link, network,transport, session, application and presentation layer. The physicallayer transmits bits over a communication link. The data link layertransmits error free frames of data. The network layer transmits androutes data packets.

For downstream data transmission, CM 16 is connected to cable network 14in a physical layer 38 via a Radio Frequency (“RF”) Interface 40. In apreferred embodiment of the present invention, RF Interface 40 has anoperation frequency range of 50 Mega-Hertz (“MHz”) to 1 Giga-Hertz(“GHz”) and a channel bandwidth of 6 MHz. However, other operationfrequencies may also be used and the invention is not limited to thesefrequencies. RF interface 40 uses a signal modulation method ofQuadrature Amplitude Modulation (“QAM”). As is known in the art, QAM isused as a means of encoding digital information over radio, wire, orfiber optic transmission links. QAM is a combination of amplitude andphase modulation and is an extension of multiphase phase-shift-keying.QAM can have any number of discrete digital levels typically including4, 16, 64 or 256 levels. In one embodiment of the present invention,QAM-64 is used in RF interface 40. However, other operating frequenciesmodulation methods could also be used. For more information on RFinterface 40 see the Institute of Electrical and Electronic Engineers(“IEEE”) standard 802.14 for cable modems incorporated herein byreference. IEEE standards can be found on the World Wide Web at theUniversal Resource Locator (“URL”) “www.ieee.org.” However, other RFinterfaces 40 could also be used and the present invention is notlimited to IEEE 802.14 (e.g., RF interfaces from Multimedia CableNetwork Systems (“MCNS”) and others could also be used).

Above RF interface 40 in a data-link layer 42 is a Medium Access Control(“MAC”) layer 44. As is known in the art, MAC layer 44 controls accessto a transmission medium via physical layer 38. For more information onMAC layer protocol 44 see IEEE 802.14 for cable modems. However, otherMAC layer protocols 44 could also be used and the present invention isnot limited to IEEE 802.14 MAC layer protocols (e.g., MCNS MAC layerprotocols and others could also be used).

Above MAC layer 44 is an optional link security protocol stack 46. Linksecurity protocol stack 46 prevents unauthorized users from making adata connection from cable network 14. RF interface 40 and MAC layer 44can also be used for an upstream connection if data-over-cable system 10is used without telephony return.

For upstream data transmission with telephony return, CM 16 is connectedto PSTN 22 in physical layer 38 via modem interface 48. TheInternational Telecommunications Union-Telecommunication StandardizationSector (“ITU-T”, formerly known as the CCITT) defines standards forcommunication devices identified by “V.xx” series where “xx” is anidentifying number. ITU-T standards can be found on the World Wide Webat the URL “www.itu.ch.”

In one embodiment of the present invention, ITU-T V.34 is used as modeminterface 48. As is known in the art, ITU-T V.34 is commonly used in thedata link layer for modem communications and currently allows data ratesas high as 33,600 bits-per-second (“bps”). For more information see theITU-T V.34 standard. However, other modem interfaces or other telephonyinterfaces could also be used.

Above modem interface 48 in data link layer 42 is Point-to-PointProtocol (“PPP”) layer 50, hereinafter PPP 50. As is known in the art,PPP is used to encapsulate network layer datagrams over a serialcommunications link. For more information on PPP see InternetEngineering Task Force (“IETF”) Request for Comments (“RFC”), RFC-1661,RFC-1662 and RFC-1663 incorporated herein by reference. Information forIETF RFCs can be found on the World Wide Web at URLs “ds.internic.net”or “www.ietf.org.”

Above both the downstream and upstream protocol layers in a networklayer 52 is an Internet Protocol (“IP”) layer 54. IP layer 54,hereinafter IP 54, roughly corresponds to OSI layer 3, the networklayer, but is typically not defined as part of the OSI model. As isknown in the art, IP 54 is a routing protocol designed to route trafficwithin a network or between networks. For more information on IP 54 seeRFC-791 incorporated herein by reference.

Internet Control Message Protocol (“ICMP”) layer 56 is used for networkmanagement. The main functions of ICMP layer 56, hereinafter ICMP 56,include error reporting, reachability testing (e.g., “pinging”)congestion control, route-change notification, performance, subnetaddressing and others. Since IP 54 is an unacknowledged protocol,datagrams may be discarded and ICMP 56 is used for error reporting. Formore information on ICMP 56 see RFC-971 incorporated herein byreference.

Above IP 54 and ICMP 56 is a transport layer 58 with User DatagramProtocol layer 60 (“UDP”). UDP layer 60, hereinafter UDP 60, roughlycorresponds to OSI layer 4, the transport layer, but is typically notdefined as part of the OSI model. As is known in the art, UDP 60provides a connectionless mode of communications with datagrams. Formore information on UDP 60 see RFC-768 incorporated herein by reference.

Above the network layer are a Simple Network Management Protocol(“SNMP”) layer 62, Trivial File Protocol (“TFTP”) layer 64, Dynamic HostConfiguration Protocol (“DHCP”) layer 66 and a UDP manager 68. SNMPlayer 62 is used to support network management functions. For moreinformation on SNMP layer 62 see RFC-1157 incorporated herein byreference. TFTP layer 64 is a file transfer protocol used to downloadfiles and configuration information. For more information on TFTP layer64 see RFC-1350 incorporated herein by reference. DHCP layer 66 is aprotocol for passing configuration information to hosts on an IP 54network. For more information on DHCP layer 66 see RFC-1541 and RFC-2131incorporated herein by reference. UDP manager 68 distinguishes androutes packets to an appropriate service (e.g., a virtual tunnel). Moreor few protocol layers could also be used with data-over-cable system10.

CM 16 supports transmission and reception of IP 54 datagrams asspecified by RFC-791. CMTS 12 and TRAC 24 may perform filtering of IP 54datagrams. CM 16 is configurable for IP 54 datagram filtering torestrict CM 16 and CPE 18 to the use of only their assigned IP 54addresses. CM 16 is configurable for IP 54 datagram UDP 60 portfiltering (i.e., deep filtering).

CM 16 forwards IP 54 datagrams destined to an IP 54 unicast addressacross cable network 14 or PSTN 22. Some routers have security featuresintended to filter out invalid users who alter or masquerade packets asif sent from a valid user. Since routing policy is under the control ofnetwork operators, such filtering is a vendor specific implementation.For example, dedicated interfaces (i.e., Frame Relay) may exist betweenTRAC 24 and CMTS 12 which preclude filtering, or various forms ofvirtual tunneling and reverse virtual tunneling could be used tovirtually source upstream packets from CM 16. For more information onvirtual tunneling see Level 2 Tunneling Protocol (“L2TP”) orPoint-to-Point Tunneling Protocol (“PPTP”) in IETF draft documentsincorporated herein by reference by Kory Hamzeh, et. al (IETF draftdocuments are precursors to IETF RFCs and are works in progress).

CM 16 also forwards IP 54 datagrams destined to an IP 54 multicastaddress across cable network 14 or PSTN 22. CM 16 is configurable tokeep IP 54 multicast routing tables and to use group membershipprotocols. CM 16 is also capable of IP 54 tunneling upstream through thetelephony path. A CM 16 that wants to send a multicast packet across avirtual tunnel will prepend another IP 54 header, set the destinationaddress in the new header to be the unicast address of CMTS 12 at theother end of the tunnel, and set the IP 54 protocol field to be four,which means the next protocol is IP 54.

CMTS 12 at the other end of the virtual tunnel receives the packet,strips off the encapsulating IP 54 header, and forwards the packet asappropriate. A broadcast IP 54 capability is dependent upon theconfiguration of the direct linkage, if any, between TRAC 24 and CMTS12. CMTS 12, CM 16, and TRAC 24 are capable of routing IP 54 datagramsdestined to an IP 54 broadcast address which is across cable network 14or PSTN 22 if so configured. CM 16 is configurable for IP 54 broadcastdatagram filtering.

An operating environment for CM 16 of the present invention includes aprocessing system with at least one high speed Central Processing Unit(“CPU”) and a memory system. In accordance with the practices of personsskilled in the art of computer programming, the present invention isdescribed below with reference to acts and symbolic representations ofoperations that are performed by the processing system, unless indicatedotherwise. Such acts and operations are sometimes referred to as being“computer-executed”, or “CPU executed.”

It will be appreciated that the acts and symbolically representedoperations include the manipulation of electrical signals by the CPU. Aselectrical system with data bits causes a resulting transformation orreduction of the electrical signal representation, and the maintenanceof data bits at memory locations in the memory system to therebyreconfigure or otherwise alter the CPU's operation, as well as otherprocessing of signals. The memory locations where data bits aremaintained are physical locations that have particular electrical,magnetic, optical, or organic properties corresponding to the data bits.

The data bits may also be maintained on a computer readable mediumincluding magnetic disks, optical disks, organic disks, and any othervolatile or non-volatile mass storage system readable by the CPU. Thecomputer readable medium includes cooperating or interconnected computerreadable media, which exist exclusively on the processing system or isdistributed among multiple interconnected processing systems that may belocal or remote to the processing system.

Initialization of a Cable Modem With Telephony Return

When CM 16 is initially powered on, if telephony return is being used,CM 16 will receive a Telephony Channel Descriptor (“TCD”) from CMTS 12that is used to provide dialing and access instructions on downstreamchannels via cable network 14. Information in the TCD is used by CM 16to connect to TRAC 24. The TCD is transmitted as a MAC managementmessage with a management type value of TRI_TCD at a periodic interval(e.g., every 2 seconds). To provide for flexibility, the TCD messageparameters are encoded in a Type/Length/Value (“TLV”) form. However,other encoding techniques could also be used. FIG. 3 is a block diagramillustrating a TCD message structure 70 with MAC 44 management header 72and Service Provider Descriptor(s) (“SPD”) 74 encoded in TLV format.SPDs 74 are compound TLV encodings that define telephony physical-layercharacteristics that are used by CM 16 to initiate a telephone call. SPD74 is a TLV-encoded data structure that contains sets of dialing andaccess parameters for CM 16 with telephony return. SPD 74 is containedwithin TCD message 70. There may be multiple SPD 74 encodings within asingle TCD message 70. There is at least one SPD 74 in TCD message 70.SPD 74 parameters are encoded as SPD-TLV tuples. SPD 74 contains theparameters shown in Table 1 and may contain optional vendor specificparameters. However, more or fewer parameters could also be used in SPD74.

TABLE 1 SPD 74 Parameter Description Factory Default Flag Boolean value,if TRUE(1), indicates a SPD which should be used by CM 16. ServiceProvider Name This parameter includes the name of a service provider.Format is standard ASCII string composed of numbers and letters.Telephone Numbers These parameters contain telephone numbers that CM 16uses to initiate a telephony modem link during a login process.Connections are attempted in ascending numeric order (i.e., Phone Number1, Phone Number 2 . . .). The SPD contains a valid telephony dial stringas the primary dial string (Phone Number 1), secondary dial-strings areoptional. Format is ASCII string(s) composed of: any sequence ofnumbers, pound “#” and star “*” keys and comma character “,” used toindicate a two second pause in dialing. Connection Threshold The numberof sequential connection failures before indicating connection failure.A dial attempt that does not result in an answer and connection after nomore than ten rings is considered a failure. The default value is one.Login User Name This contains a user name CM 16 will use anauthentication protocol over the telephone link during theinitialization procedure. Format is a monolithic sequence ofalphanumeric characters in an ASCII string composed of numbers andletters. Login Password This contains a password that CM 16 will useduring authentication over a telephone link during the initializationprocedure. Format is a monolithic sequence of alphanumeric characters inan ASCII string composed of numbers and letters. DHCP AuthenticateBoolean value, reserved to indicate that CM 16 uses a specific indicatedDHCP 66 Server (see next parameter) for a DHCP 66 Client and BOOTP RelayProcess when TRUE (one). The default is FALSE (zero) which allows anyDHCP 66 Server. DHCP Server IP 54 address value of a DHCP 66 Server CM16 uses for DHCP 66 Client and BOOTP Relay Process. If this attribute ispresent and DHCP 66 Authenticate attribute is TRUE(1). The default valueis integer zero. RADIUS Realm The realm name is a string that defines aRADIUS server domain. Format is a monolithic sequence of alphanumericcharacters in an ACSII string composed of numbers and letters. PPPAuthentication This parameter instructs the telephone modem whichauthentication procedure to perform over the telephone link. Demand DialTimer This parameter indicates time (in seconds) of inactive networkingtime that will be allowed to elapse before hanging up a telephoneconnection at CM 16. If this optional parameter is not present, or setto zero, then the demand dial feature is not activated. The defaultvalue is zero. Vendor Specific Extensions Optional vendor specificextensions.

A Termination System Information (“TSI”) message is transmitted by CMTS12 at periodic intervals (e.g., every 2 seconds) to report CMTS 12information to CM 16 whether or not telephony return is used. The TSImessage is transmitted as a MAC 44 management message. The TSI providesa CMTS 12 boot record in a downstream channel to CM 16 via cable network14. Information in the TSI is used by CM 16 to obtain information aboutthe status of CMTS 12. The TSI message has a MAC 44 management typevalue of TRI_TSI.

FIG. 4 is a block diagram of a TSI message structure 76. TSI messagestructure 76 includes a MAC 44 management header 78, a downstreamchannel IP address 80, a registration IP address 82, a CMTS 12 boot time84, a downstream channel identifier 86, an epoch time 88 and vendorspecific TLV encoded data 90.

A description of the fields of TSI message 76 are shown in Table 2.However, more or fewer fields could also be used in TSI message 76.

TABLE 2 TSI 76 Parameter Description Downstream Channel This fieldcontains an IP 54 address of IP Address 80 CMTS 12 available on thedownstream channel this message arrived on. Registration IP Address 82This field contains an IP 54 address CM 16 sends its registrationrequest messages to. This address MAY be the same as the DownstreamChannel IP 54 address. CMTS Boot Time 84 Specifies an absolute-time of aCMTS 12 recorded epoch. The clock setting for this epoch uses thecurrent clock time with an unspecified accuracy. Time is represented asa 32 bit binary number. Downstream Channel ID 86 A downstream channel onwhich this message has been transmitted. This identifier is arbitrarilychosen by CMTS 12 and is unique within the MAC 44 layer. Epoch 88 Aninteger value that is incremented each time CMTS 12 is either re-initialized or performs address or routing table flush. Vendor SpecificExtensions 90 Optional vendor extensions may be added as TLV encodeddata.

After receiving TCD 70 message and TSI message 76, CM 16 continues toestablish access to data network 28 (and resources on the network) byfirst dialing into TRAC 24 and establishing a telephony PPP 50 session.Upon the completion of a successful PPP 50 connection, CM 16 performsPPP Link Control Protocol (“LCP”) negotiation with TRAC 24. Once LCPnegotiation is complete, CM 16 requests Internet Protocol ControlProtocol (“IPCP”) address negotiation. For more information on IPCP seeRFC-1332 incorporated herein by reference. During IPCP negotiation, CM16 negotiates an IP 54 address with TRAC 24 for sending IP 54 datapacket responses back to data network 28 via TRAC 24.

When CM 16 has established an IP 54 link to TRAC 24, it begins“upstream” communications to CMTS 12 via DHCP layer 66 to complete avirtual data connection by attempting to discover network hostinterfaces available on CMTS 12 (e.g., IP 54 host interfaces for avirtual IP 54 connection). The virtual data connection allows CM 16 toreceive data from data network 28 via CMTS 12 and cable network 14, andsend return data to data network 28 via TRAC 24 and PSTN 22. CM 16 mustfirst determine an address of a host interface (e.g., an IP 54interface) available on CMTS 12 that can be used by data network 28 tosend data to CM 16. However, CM 16 has only a downstream connection fromCMTS 12 and has to obtain a connection address to data network 28 usingan upstream connection to TRAC 24.

Addressing Network Host Interfaces in the Data-over-cable System via theCable Modem

FIG. 5 is a flow diagram illustrating a method 92 for addressing networkhost interfaces in a data-over-cable system with telephony return via acable modem. Method 92 allows a cable modem to establish a virtual dataconnection to a data network. In method 92, multiple network devices areconnected to a first network with a downstream connection of a firstconnection type, and connected to a second network with an upstreamconnection of a second connection type. The first and second networksare connected to a third network with a third connection type.

At step 94, a selection input is received on a first network device fromthe first network over the downstream connection. The selection inputincludes a first connection address allowing the first network device tocommunicate with the first network via upstream connection to the secondnetwork. At step 96, a first message of a first type for a firstprotocol is created on the first network device having the firstconnection address from the selection input in a first message field.The first message is used to request a network host interface address onthe first network. The first connection address allows the first networkdevice to have the first message with the first message type forwardedto network host interfaces available on the first network via theupstream connection to the second network.

At step 98, the first network device sends the first message over theupstream connection to the second network. The second network uses thefirst address field in the first message to forward the first message toone or more network host interfaces available on first network at step100. Network host interfaces available on the first network that canprovide the services requested in first message send a second messagewith a second message type with a second connection address in a secondmessage field to the first network at step 102. The second connectionaddress allows the first network device to receive data packets from thethird network via a network host interface available on the firstnetwork. The first network forwards one or more second messages on thedownstream connection to the first network device at step 104.

The first network device selects a second connection address from one ofthe second messages from one of the one or more network host interfacesavailable on the first network at step 106 and establishes a virtualconnection from the third network to the first network device using thesecond connection address for the selected network host interface.

The virtual connection includes receiving data on the first network hostinterface on the first network from the third network and sending thedata over the downstream connection to the first network device. Thefirst network device sends data responses back to the third network overthe upstream connection to the second network, which forwards the datato the appropriate destination on the third network.

In one embodiment of the present invention, the data-over-cable systemis data-over-cable system 10, the first network device is CM 16, thefirst network is cable television network 14, the downstream connectionis a cable television connection. The second network is PSTN 22, theupstream connection is a telephony connection, the third network is datanetwork 28 (e.g., the Internet or an intranet) and the third type ofconnection is an IP 54 connection. The first and second connectionaddresses are IP 54 addresses. However, the present invention is notlimited to the network components and addresses described. Method 92allows CM 16 to determine an IP 54 network host interface addressavailable on CMTS 12 to receive IP 54 data packets from data network 28,thereby establishing a virtual IP 54 connection with data network 28.

After addressing network host interfaces using method 92, an exemplarydata path through cable system 10 is illustrated in Table 3. Howeverother data paths could also be used and the present invention is notlimited to the data paths shown in Table 3. For example, CM 16 may senddata upstream back through cable network 14 (e.g., CM 16 to cablenetwork 14 to CMTS 12) and not use PSTN 22 and the telephony returnupstream path.

TABLE 3 1. An IP 54 datagram from data network 28 destined for CM 16arrives on CMTS-NSI 32 and enters CMTS 12. 2. CMTS 12 encodes the IP 54datagram in a cable data frame, passes it to MAC 44 and transmits it“downstream” to RF interface 40 on CM 16 via cable network 14. 3. CM 16recognizes the encoded IP 54 datagram in MAC layer 44 received via RFinterface 40. 4. CM 16 responds to the cable data frame and encapsulatesa response IP 54 datagram in a PPP 50 frame and transmits it “upstream”with modem interface 48 via PSTN 22 to TRAC 24. 5. TRAC 24 decodes theIP 54 datagram and forwards it via TRAC-NSI 30 to a destination on datanetwork 28.

Dynamic Network Host Configuration on Data-over-cable System

As was illustrated in FIG. 2, CM 16 includes a Dynamic HostConfiguration Protocol (“DHCP”) layer 66, hereinafter DHCP 66. DHCP 66is used to provide configuration parameters to hosts on a network (e.g.,an IP 54 network). DHCP 66 consists of two components: a protocol fordelivering host-specific configuration parameters from a DHCP 66 serverto a host and a mechanism for allocation of network host addresses tohosts. DHCP 66 is built on a client-server model, where designated DHCP66 servers allocate network host addresses and deliver configurationparameters to dynamically configured network host clients.

FIG. 6 is a block diagram illustrating a DHCP 66 message structure 108.The format of DHCP 66 messages is based on the format of BOOTstrapProtocol (“BOOTP”) messages described in RFC-951 and RFC-1542incorporated herein by reference. From a network host client's point ofview, DHCP 66 is an extension of the BOOTP mechanism. This behaviorallows existing BOOTP clients to interoperate with DHCP 66 serverswithout requiring any change to network host the clients' BOOTPinitialization software. DHCP 66 provides persistent storage of networkparameters for network host clients.

To capture BOOTP relay agent behavior described as part of the BOOTPspecification and to allow interoperability of existing BOOTP clientswith DHCP 66 servers, DHCP 66 uses a BOOTP message format. Using BOOTPrelaying agents eliminates the necessity of having a DHCP 66 server oneach physical network segment.

DHCP 66 message structure 108 includes an operation code field 110(“op”), a hardware address type field 112 (“htype”), a hardware addresslength field 114 (“hlen”), a number of hops field 116 (“hops”), atransaction identifier field 118 (“xid”), a seconds elapsed time field120 (“secs”), a flags field 122 (“flags”), a client IP address field 124(“ciaddr”), a your IP address field 126 (“yiaddr”), a server IP addressfield 128 (“siaddr”), a gateway/relay agent IP address field 130(“giaddr”), a client hardware address field 132 (“chaddr”), an optionalserver name field 134 (“sname”), a boot file name 136 (“file”) and anoptional parameters field 138 (“options”). Descriptions for DHCP 66message 108 fields are shown in Table 4.

TABLE 4 DCHP 66 Parameter Description OP 110 Message op code/messagetype. 1 BOOTREQUEST, 2 = BOOTREPLY. HTYPE 112 Hardware address type(e.g., ‘1’ = 10 Mps Ethernet). HLEN 114 Hardware address length (e.g.,‘6’ for 10 Mbps Ethernet). HOPS 116 Client sets to zero, optionally usedby relay-agents when booting via a relay-agent. XID 118 Transaction ID,a random number chosen by the client, used by the client and server toassociate messages and responses between a client and a server. SECS 120Filled in by client, seconds elapsed since client started trying toboot. FLAGS 122 Flags including a BROADCAST bit. CIADDR 124 Client IPaddress; filled in by client in DHCPREQUEST if verifying previouslyallocated configuration parameters. YIADDR 126 ‘Your’(client) IPaddress. SIADDR 128 IP 54 address of next server to use in bootstrap;returned in DHCPOFFER, DHCPACK and DHCPNAK by server. GIADDR 130 Gatewayrelay agent IP 54 address, used in booting via a relay-agent. CHADDR 132Client hardware address (e.g., MAC layer 44 address). SNAME 134 Optionalserver host name, null terminated string. FILE 136 Boot file name,terminated by a null string. OPTIONS 138 Optional parameters.

The DHCP 66 message structure shown in FIG. 6 is used to discover IP 54and other network host interfaces in data-over-cable system 10. Anetwork host client (e.g., CM 16) uses DHCP 66 to acquire or verify anIP 54 address and network parameters whenever the network parameters mayhave changed. Table 5 illustrates a typical use of the DHCP 66 protocolto discover a network host interface from a network host client.

TABLE 5 1. A network host client broadcasts a DHCP 66 discover messageon its local physical subnet. The DHCP 66 discover message may includeoptions that suggest values for a network host interface address. BOOTPrelay agents may pass the message on to DHCP 66 servers not on the samephysical subnet. 2. DHCP servers may respond with a DHCPOFFER messagethat includes an available network address in the ‘yiaddr’ field (andother configuration parameters in DHCP 66 options) from a network hostinterface. DHCP 66 servers unicasts the DHCPOFFER message to the networkhost client (using the DHCP/BOOTP relay agent if necessary) if possible,or may broadcast the message to a broadcast address (preferably255.255.255.255) on the client's subnet. 3. The network host clientreceives one or more DHCPOFFER messages from one or more DHCP 66servers. The network host client may choose to wait for multipleresponses. 4. The network host client chooses one DHCP 66 server with anassociated network host interface from which to request configurationparameters, based on the configuration parameters offered in theDHCPOFFER messages.

Discovering Network Host Interfaces in the Data-over-cable System

The DHCP discovery process illustrated in table 5 will not work indata-over-cable system 10. CM 16 has only a downstream connection fromCMTS 12, which includes DHCP 66 servers, associated with network hostinterfaces available on CMTS 12. In a preferred embodiment of thepresent invention, CM 16 discovers network host interfaces via TRAC 24and PSTN 22 on an upstream connection.

The DHCP 66 addressing process shown in Table 5 was not originallyintended to discover network host interfaces in data-over-cable system10. CMTS 12 has DHCP 66 servers associated with network host interfaces(e.g., IP interfaces), but CM 16 only has as downstream connection fromCMTS 12. CM 16 has an upstream connection to TRAC 24, which has a DHCP66 layer. However, TRAC 24 does not have DHCP 66 servers, or directaccess to network host interfaces on CMTS 12. FIGS. 7A and 7B are a flowdiagram illustrating a method 140 for discovering network hostinterfaces in data-over-cable system 10. When CM 16 has established anIP 54 link to TRAC 24, it begins communications with CMTS 12 via DHCP 66to complete a virtual IP 54 connection with data network 28. However, todiscover what IP 54 host interfaces might be available on CMTS 12, CM 16has to communicate with CMTS 12 via PSTN 22 and TRAC 24 since CM 16 onlyhas a “downstream” cable channel from CMTS 12.

At step 142 in FIG. 7A, after receiving a TSI message 76 from CMTS 12 ona downstream connection, CM 16 generates a DHCP discover(“DHCPDISCOVER”) message and sends it upstream via PSTN 22 to TRAC 22 todiscover what IP 54 interfaces are available on CMTS 12. The fields ofthe DHCP discover message are set as illustrated in Table 6. However,other field settings may also be used.

TABLE 6 DHCP 66 Parameter Description OP 110 Set to BOOTREQUEST. HTYPE112 Set to network type (e.g., one for 10 Mbps Ethernet). HLEN 114 Setto network length (e.g., six for 10 Mbps Ethernet) HOPS 116 Set to zero.FLAGS 122 Set BROADCAST bit to zero. CIADDR 124 If CM 16 has previouslybeen assigned an IP 54 address, the IP 54 address is placed in thisfield. If CM 16 has previously been assigned an IP 54 address by DHCP66, and also has been assigned an address via IPCP, CM 16 places theDHCP 66 IP 54 address in this field. GIADDR 130 CM 16 places theDownstream Channel IP 54 address 80 of CMTS 12 obtained in TSI message76 on a cable downstream channel in this field. CHADDR 132 CM 16 placesits 48-bit MAC 44 LAN address in this field.

The DHCPDISCOVER message is used to “discover” the existence of one ormore IP 54 host interfaces available on CMTS 12. DHCP 66 giaddr-field130 (FIG. 6) includes the downstream channel IP address 80 of CMTS 12obtained in TSI message 76 (e.g., the first message field from step 96of method 92). Using the downstream channel IP address 80 of CMTS 12obtained in TSI message 76 allows the DHCPDISCOVER message to beforwarded by TRAC 24 to DHCP 66 servers (i.e., protocol servers)associated with network host interfaces available on CMTS 12. If DHCP 66giaddr-field 130 (FIG. 6) in a DHCP message from a DHCP 66 client isnon-zero, the DHCP 66 server sends any return messages to a DHCP 66server port on a DHCP 66 relaying agent (e.g., CMTS 12) whose addressappears in DHCP 66 giaddr-field 130.

In a typical DHCP 66 discovery process the DHCP 66 giaddr-field 130 isset to zero. In a typical DHCP 66 discovery process the DHCP 66giaddr-field 130 is set to zero. However, in a preferred embodiment ofthe present invention, the giaddr-field 130 contains the IP address 80of CMTS 12. If DHCP 66 giaddr-field 130 is zero, the DHCP 66 client ison the same subnet as the DHCP 66 server, and the DHCP 66 server sendsany return messages to either the DHCP 66 client's network address, ifthat address was supplied in DHCP 66 ciaddr-field 124 (FIG. 6), or to aclient's hardware address specified in DHCP 66 chaddr-field 132 (FIG. 6)or to a local subnet broadcast address (e.g., 255.255.255.255).

At step 144, a DHCP 66 layer on TRAC 24 broadcasts the DHCPDISCOVERmessage on its local network leaving DHCP 66 giaddr-field 130 intactsince it already contains a non-zero value. TRAC's 24 local networkincludes connections to one or more DHCP 66 proxies (i.e., network hostinterface proxies). The DHCP 66 proxies accept DHCP 66 messagesoriginally from CM 16 destined for DHCP 66 servers connected to networkhost interfaces available on CMTS 12 since TRAC 24 has no direct accessto DCHP 66 servers associated with network host interfaces available onCMTS 12. DHCP 66 proxies are not used in a typical DHCP 66 discoveryprocess.

One or more DHCP 66 proxies on TRAC's 24 local network recognizes theDHCPDISCOVER message and forwards it to one or more DHCP 66 serversassociated with network host interfaces (e.g., IP 54 interfaces)available on CMTS 12 at step 146. Since DHCP 66 giaddr-field 130 (FIG.6) in the DHCPDISCOVER message sent by CM 16 is already non-zero (i.e.,contains the downstream IP address of CMTS 12), the DHCP 66 proxies alsoleave DHCP 66 giaddr-field 130 intact.

One or more DHCP 66 servers for network host interfaces (e.g., IP 54interfaces) available on CMTS 12 receive the DHCPDISCOVER message andgenerate a DHCP 66 offer message (“DHCPOFFER”) at step 148. The DHCP 66offer message is an offer of configuration parameters sent from networkhost interfaces to DHCP 66 servers and back to a network host client(e.g., CM 16) in response to a DHCPDISCOVER message. The DHCP 66 offermessage is sent with the message fields set as illustrated in Table 7.However, other field settings can also be used. DHCP 66 yiaddr-field 126(e.g., second message field from step 102 of method 92) contains an IP54 address for a network host interface available on CMTS 12 and usedfor receiving data packets from data network 28.

TABLE 7 DHCP 66 Parameter Description FLAGS 122 BROADCAST bit set tozero. YIADDR 126 IP 54 address from a network host interface to allow CM16 to receive data from data network 28 via a network host interfaceavailable on CMTS 12. SIADDR 128 An IP 54 address for a TFTP 64 serverto download configuration information for an interface host. CHADDR 132MAC 44 address of CM 16. SNAME 134 Optional DHCP 66 server identifierwith an interface host. FILE 136 A TFTP 64 configuration file name forCM 16.

DHCP 66 servers send the DHCPOFFER message to the address specified in66 giaddr-field 130 (i.e., CMTS 12) from the DHCPDISCOVER message ifassociated network host interfaces (e.g., IP 54 interfaces) can offerthe requested service (e.g., IP 54 service) to CM 16. The DHCPDISOVERmessage DHCP 66 giaddr-field 130 contains a downstream channel IPaddress 80 of CMTS 12 that was received by CM 16 in TSI message 76. Thisallows CMTS 12 to receive the DHCPOFFER messages from the DHCP 66servers and send them to CM 16 via a downstream channel on cable network14.

At step 150 in FIG. 7B, CMTS 12 receives one or more DHCPOFFER messagesfrom one or more DHCP 66 servers associated with the network hostinterfaces (e.g., IP 54 interfaces). CMTS 12 examines DHCP 66yiaddr-field 126 and DHCP 66 chaddr-field 132 in the DHCPOFFER messagesand sends the DHCPOFFER messages to CM 16 via cable network 14. DHCP 66yiaddr-field 126 contains an IP 54 address for a network host IP 54interface available on CMTS 12 and used for receiving IP 54 data packetsfrom data network 28. DHCP 66 chaddr-field 132 contains the MAC 44 layeraddress for CM 16 on a downstream cable channel from CMTS 12 via cablenetwork 14. CMTS 12 knows the location of CM 16 since it sent CM 16 aMAC 44 layer address in one or more initialization messages (e.g., TSImessage 76).

If a BROADCAST bit in flags field 124 is set to one, CMTS 12 sends theDHCPOFFER messages to a broadcast IP 54 address (e.g., 255.255.255.255)instead of the address specified in DHCP 66 yiaddr-field 126. DHCP 66chaddr-field 132 is still used to determine that MAC 44 layer address.If the BROADCAST bit in DHCP 66 flags field 122 is set, CMTS 12 does notupdate internal address or routing tables based upon DHCP 66yiaddr-field 126 and DHCP 66 chaddr-field 132 pair when a broadcastmessage is sent.

At step 152, CM 16 receives one or more DHCPOFFER messages from CMTS 12via cable network 14 on a downstream connection. At step 154, CM 16selects an offer for IP 54 service from one of the network hostinterfaces (e.g., an IP interfaces 54) available on CMTS 12 thatresponded to the DHCPDISOVER message sent at step 142 in FIG. 7A andestablishes a virtual IP 54 connection. The selected DHCPOFFER messagecontains a network host interface address (e.g., IP 54 address) in DHCP66 yiaddr-field 126 (FIG. 6). A cable modem acknowledges the selectednetwork host interface with DHCP 66 message sequence explained below.

After selecting and acknowledging a network host interface, CM 16 hasdiscovered an IP 54 interface address available on CMTS 12 forcompleting a virtual IP 54 connection with data network 28.Acknowledging a network host interface is explained below. The virtualIP 54 connection allows IP 54 data from data network 28 to be sent toCMTS 12 which forwards the IP 54 packets to CM 16 on a downstreamchannel via cable network 14. CM 16 sends response IP 54 packets back todata network 28 via PSTN 22 and TRAC 24.

FIG. 8 is a block diagram illustrating a data-over-cable system 156 forthe method illustrated in FIGS. 7A and 7B. Data-over-cable system 156includes DHCP 66 proxies 158, DHCP 66 servers 160 and associated NetworkHost Interfaces 162 available on CMTS 12. Multiple DHCP 66 proxies 158,DHCP 66 servers 160 and network host interfaces 162 are illustrated assingle boxes in FIG. 8. FIG. 8 also illustrates DHCP 66 proxies 158separate from TRAC 24. In one embodiment of the present invention, TRAC24 includes DHCP 66 proxy functionality and no separate DHCP 66 proxies158 are used. In such an embodiment, TRAC 24 forwards DHCP 66 messagesusing DHCP 66 giaddr-field 130 to DHCP 66 servers 160 available on CMTS12. FIG. 9 is a block diagram illustrating a message flow 164 of method140 (FIGS. 7A and 7B).

Message flow 164 includes DHCP proxies 158 and DHCP servers 160illustrated in FIG. 8 Steps 142, 144, 146, 148, 150 and 154 of method140 (FIGS. 7A and 7B) are illustrated in FIG. 9. In one embodiment ofthe present invention, DHCP proxies 158 are not separate entities, butare included in TRAC 24. In such an embodiment, DHCP proxy services areprovided directly by TRAC 24.

Resolving Addresses For Network Host Interfaces

Since CM 16 receives multiple DHCPOFFER messages (Step 152FIG. 7B) CM 16resolves and acknowledges one offer from a selected network hostinterface. FIGS. 10A and 10B are a flow diagram illustrating a method166 for resolving and acknowledging host addresses in a data-over-cablesystem. Method 166 includes a first network device that is connected toa first network with a downstream connection of a first connection type,and connected to a second network with an upstream connection of asecond connection type. The first and second networks are connected to athird network with a third connection type. In one embodiment of thepresent invention, the first network device is CM 16, the first networkis cable network 14, the second network is PSTN 22 and the third networkis data network 28 (e.g., the Internet). The downstream connection is acable television connection, the upstream connection is a telephonyconnection, and the third connection is an IP connection.

Turning to FIG. 10A, one or more first messages are received on thefirst network device from the first network on the downstream connectionat step 168. The one or more first messages are offers from one or morenetwork host interfaces available on the first network to provide thefirst network device a connection to the third network. The firstnetwork device selects one of the network host interfaces using messagefields in one of the one or more first messages at step 170. The firstnetwork device creates a second message with a second message type toaccept the offered services from a selected network host interface atstep 172. The second message includes a connection address for the firstnetwork in a first message field and an identifier to identify theselected network host interface in a second message field.

The first network device sends the second message over the upstreamconnection to the second network at step 174. The second network usesthe first message field in the second message to forward the secondmessage to the one or more network host interfaces available on firstnetwork at step 176.

A network host interface available on the first network identified insecond message field in the second message from the first network devicerecognizes an identifier for the network host interface at 178 in FIG.10B. The selected network host interface sends a third message with athird message type to the first network at step 180. The third messageis an acknowledgment for the first network device that the selectednetwork host interface received the second message from the firstnetwork device. The first network stores a connection address for theselected network interface in one or more tables on the first network atstep 182. The first network will forward data from the third network tothe first network device when it is received on the selected networkhost interface using the connection address in the one or more routingtables. The first network forwards the third message to the firstnetwork device on the downstream connection at step 184. The firstnetwork device receives the third message at step 186. The first networkand the first network device have the necessary addresses for a virtualconnection that allows data to be sent from the third network to anetwork host interface on the first network, and from the first networkover the downstream connection to the first network device. Method 166accomplishes resolving network interface hosts addresses from a cablemodem in a data-over-cable with telephony return.

Method 166 of the present invention is used in data-over-cable system 10with telephony return. However, the present invention is not limited todata-over-cable system 10 with telephony return and can be used indata-over-cable system 10 without telephony return by using an upstreamcable channel instead of an upstream telephony channel.

FIGS. 11A and 11B are a flow diagram illustrating a method 188 forresolving discovered host addresses in data-over-cable system 10 withtelephony return. At step 190 in FIG. 11A, CM 16 receives one or moreDHCPOFFER messages from one or more DHCP 66 servers associated with oneor more network host interfaces (e.g., at step 168 in method 166). Theone or more DHCPOFFER messages include DHCP 66 fields set as illustratedin Table 7 above. However, other field settings could also be used. Atstep 192, CM 16 selects one of the DHCPOFFER messages (see also, step170 in method 166). At step 194, CM 16 creates a DHCP 66 request message(“DHCPREQUEST”) message to request the services offered by a networkhost interface selected at step 192. The fields of the DHCP requestmessage are set as illustrated in Table 8. However, other field settingsmay also be used.

TABLE 8 DHCP 66 Parameter Description OP 110 Set to BOOTREQUEST. HTYPE112 Set to network type (e.g., one for 10 Mbps Ethernet). HLEN 114 Setto network length (e.g., six for 10 Mbps Ethernet) HOPS 116 Set to zero.FLAGS 118 Set BROADCAST bit to zero. CIADDR 124 If CM 16 has previouslybeen assigned an IP address, the IP address is placed in this field. IfCM 16 has previously been assigned an IP address by DHCP 66, and alsohas been assigned an address via IPCP, CM 16 places the DHCP 66 IP 54address in this field. YIADDR 126 IP 54 address sent from the selectednetwork interface host in DCHPOFFER message GIADDR 130 CM 16 places theDownstream Channel IP 54 address 80 CMTS 12 obtained in TSI message 76on a cable downstream channel in this field. CHADDR 132 CM 16 places its48-bit MAC 44 LAN address in this field. SNAME 134 DHCP 66 serveridentifier for the selected network interface host

The DHCPREQUEST message is used to “request” services from the selectedIP 54 host interface available on CMTS 12 using a DHCP 66 serverassociated with the selected network host interface. DHCP 66giaddr-field 130 (FIG. 6) includes the downstream channel IP address 80for CMTS 12 obtained in TSI message 76 (e.g., the first message-fieldfrom step 172 of method 166). Putting the downstream channel IP address80 obtained in TSI message 76 allows the DHCPREQUEST message to beforwarded by TRAC 24 to DCHP 66 servers associated with network hostinterfaces available on CMTS 12. DHCP 66 giaddr-field 126 contains anidentifier (second message field, step 172 in method 166) DHCP 66sname-field 134 contains a DHCP 66 server identifier associated with theselected network host interface.

If DHCP 66 giaddr-field 130 in a DHCP message from a DHCP 66 client isnon-zero, a DHCP 66 server sends any return messages to a DHCP 66 serverport on a DHCP 66 relaying agent (e.g., CMTS 12) whose address appearsin DHCP 66 giaddr-field 130. If DHCP 66 giaddr-field 130 is zero, theDHCP 66 client is on the same subnet as the DHCP 66 server, and the DHCP66 server sends any return messages to either the DHCP 66 client'snetwork address, if that address was supplied in DHCP 66 ciaddr-field124, or to the client's hardware address specified in DHCP 66chaddr-field 132 or to the local subnet broadcast address.

Returning to FIG. 11A at step 196, CM 16 sends the DHCPREQUEST messageon the upstream connection to TRAC 24 via PSTN 22. At step 198, a DHCP66 layer on TRAC 24 broadcasts the DHCPREQUEST message on its localnetwork leaving DHCP 66 giaddr-field 130 intact since it alreadycontains a non-zero value. TRAC's 24 local network includes connectionsto one or more DHCP 66 proxies. The DHCP 66 proxies accept DHCP 66messages originally from CM 16 destined for DHCP 66 servers associatedwith network host interfaces available on CMTS 12. In another embodimentof the present invention, TRAC 24 provides the DHCP 66 proxyfunctionality, and no separate DHCP 66 proxies are used.

The one or more DHCP 66 proxies on TRAC's 24 local network messageforwards the DHCPOFFER to one or more of the DHCP 66 servers associatedwith network host interfaces (e.g., IP 54 interfaces) available on CMTS12 at step 200 in FIG. 11B. Since DHCP 66 giaddr-field 130 in theDHCPDISCOVER message sent by CM 16 is already non-zero (i.e., containsthe downstream IP address of CMTS 12), the DHCP 66 proxies leave DHCP 66giaddr-field 130 intact.

One or more DHCP 66 servers for the selected network host interfaces(e.g., IP 54 interface) available on CMTS 12 receives the DHCPOFFERmessage at step 202. A selected DHCP 66 server recognizes a DHCP 66server identifier in DHCP 66 sname-field 134 or the IP 54 address thatwas sent in the DCHPOFFER message in the DHCP 66 yiaddr-field 126 fromthe DHCPREQUST message as being for the selected DHCP 66 server.

The selected DHCP 66 server associated with network host interfaceselected by CM 16 in the DHCPREQUEST message creates and sends a DCHP 66acknowledgment message (“DHCPACK”) to CMTS 12 at step 204. The DHCPACKmessage is sent with the message fields set as illustrated in Table 9.However, other field settings can also be used. DHCP 66 yiaddr-fieldagain contains the IP 54 address for the selected network host interfaceavailable on CMTS 12 for receiving data packets from data network 28.

TABLE 9 DHCP 66 Parameter Description FLAGS 122 Set a BROADCAST bit tozero. YIADDR 126 IP 54 address for the selected network host interfaceto allow CM 16 to receive data from data network 28. SIADDR 128 An IP 54address for a TFTP 64 server to download configuration information foran interface host. CHADDR 132 MAC 44 address of CM 16. SNAME 134 DHCP 66server identifier associated with the selected network host interface.FILE 136 A configuration file name for an network interface host.

The selected DHCP 66 server sends the DHCACK message to the addressspecified in DHCP 66 giaddr-field 130 from the DHCPREQUEST message to CM16 to verify the selected network host interface (e.g., IP 54 interface)will offer the requested service (e.g., IP 54 service).

At step 206, CMTS 12 receives the DHCPACK message from the selected DHCP66 server associated with the selected network host interface IP 54address(e.g., IP 54 interface). CMTS 12 examines DHCP 66 yiaddr-field126 and DHCP 66 chaddr-field 132 in the DHCPACK message. DHCP 66yiaddr-field 126 contains an IP 54 address for a network host IP 54interface available on CMTS 12 and used for receiving IP 54 data packetsfrom data network 28 for CM 16. DHCP 66 chaddr-field 132 contains theMAC 44 layer address for CM 16 on a downstream cable channel from CMTS12 via cable network 14.

CMTS 12 updates an Address Resolution Protocol (“ARP”) table and otherrouting tables on CMTS 12 to reflect the addresses in DHCP 66yiaddr-field 126 and DHCP 66 chaddr-field 132 at step 208. As is knownin the art, ARP allows a gateway such as CMTS 12 to forward anydatagrams from a data network such as data network 28 it receives forhosts such as CM 16. ARP is defined in RFC-826, incorporated herein byreference. CMTS 12 stores a pair of network address values in the ARPtable, the IP 54 address of the selected network host interface fromDHCP 66 yiaddr-field 126 and a Network Point of Attachment (“NPA”)address. In a preferred embodiment of the present invention, The NPAaddress is a MAC 44 layer address for CM 16 via a downstream cablechannel. The IP/NPA address pair are stored in local routing tables withthe IP/NPA addresses of hosts (e.g., CMs 16) that are attached to cablenetwork 14.

At step 210, CMTS 12 sends the DHCPACK message to CM 16 via cablenetwork 14. At step 212, CM 16 receives the DHCPACK message, and alongwith CMTS 12 has addresses for a virtual connection between data network28 and CM 16. When data packets arrive on the IP 54 address for theselected host interface they are sent to CMTS 12 and CMTS 12 forwardsthem using a NPA (i.e., MAC 44 address) from the routing tables on adownstream channel via cable network 14 to CM 16.

If a BROADCAST bit in flags field 124 is set to one in the DHCPACK, CMTS12 sends the DHCPACK messages to a broadcast IP 54 address (e.g.,255.255.255.255). DHCP 66 chaddr-field 132 is still used to determinethat MAC layer address. If the BROADCAST bit in flags field 122 is set,CMTS 12 does not update the ARP table or offer routing tables based uponDHCP 66 yiaddr-field 126 and DHCP 66 chaddr-field 132 pair when abroadcast message is sent.

FIG. 12 is a block diagram illustrating the message flow 214 of themethod 188 illustrated in FIGS. 11A and 11B. Message flow 214 includesDHCP proxies 158 and DHCP servers 160 illustrated in FIG. 8. Methodsteps 194, 196, 198, 204, 208, 210 and 212 of method 188 (FIGS. 11A and11B) are illustrated in FIG. 12. In one embodiment of the presentinvention, DHCP proxies 158 are not separate entities, but are includedin TRAC 24. In such an embodiment, DHCP proxy services are provideddirectly by TRAC 24.

After method 188, CMTS 12 has a valid IP/MAC address pair in one or moreaddress routing tables including an ARP table to forward IP 54 datapackets from data network 28 to CM 16, thereby creating a virtual IP 54data path to/from CM 16 as was illustrated in method 92 (FIG. 5) andTable 3. CM 16 has necessary parameters to proceed to the next phase ofinitialization, a download of a configuration file via TFTP 64. Once CM16 has received the configuration file and has been initialized, itregisters with CMTS 12 and is ready to receive data from data network14.

In the event that CM 16 is not compatible with the configuration of thenetwork host interface received in the DHCPACK message, CM 16 maygenerate a DHCP 66 decline message (“DHCPDECLINE”) and transmit it toTRAC 24 via PSTN 22. A DHCP 66 layer in TRAC 24 forwards the DHCPDECLINEmessage to CMTS 12. Upon seeing a DHCPDECLINE message, CMTS 12 flushesits ARP tables and routing tables to remove the now invalid IP/MACpairing. If an IP 54 address for a network host interface is returnedthat is different from the IP 54 address sent by CM 16 in theDCHCPREQUEST message, CM 16 uses the IP 54 address it receives in theDHCPACK message as the IP 54 address of the selected network hostinterface for receiving data from data network 28.

The present invention is described with respect to, but is not limitedto a data-over-cable-system with telephony return. Method 188 can alsobe used with a cable modem that has a two-way connection (i.e., upstreamand downstream) to cable network 14 and CMTS 12. In adata-over-cable-system without telephony return, CM 16 would broadcastthe DHCPREQUEST message to one or more DHCP 66 servers associated withone or more network host interfaces available on CMTS 12 using anupstream connection on data network 14 including the IP 54 address ofCMTS 12 in DHCP 66 giaddr-field 130. Method 188 accomplishes resolvingaddresses for network interface hosts from a cable modem in adata-over-cable with or without telephony return, and without extensionsto the existing DHCP protocol.

CPE Initialization in a Data-over-cable System

CPE 18 also uses DHCP 66 to generate requests to obtain IP 54 addressesto allow CPE 18 to also receive data from data network 28 via CM 16. Ina preferred embodiment of the present invention, CM 16 functions as astandard BOOTP relay agent/DHCP Proxy 158 to facilitate CPE's 18 accessto DHCP 66 server 160. FIGS. 13A and 13B are a flow diagram illustratinga method 216 for obtaining addresses for customer premise equipment. CM16 and CMTS 12 use information from method 214 to construct IP 54routing and ARP table entries for network host interfaces 162 providingdata to CMCI 20 and to CPE 18.

Method 216 in FIGS. 13A and 13B includes a data-over-cable system withtelephony return and first network device with a second network devicefor connecting the first network device to a first network with adownstream connection of a first connection type, and for connecting toa second network with an upstream connection of a second connectiontype. The first and second networks are connected to a third networkwith a third connection type.

In one embodiment of the present invention, data-over-cable system withtelephony return is data-over-cable system 10 with the first networkdevice CPE 18 and the second network device CM 16. The first network iscable television network 14, the downstream connection is a cabletelevision connection, the second network is PSTN 22, the upstreamconnection is a telephony connection, the third network is data network28 (e.g., the Internet or an intranet) and the third type of connectionis an IP 54 connection. However, the present invention is not limited tothe network components described and other network components may alsobe used. Method 216 allows CPE 18 to determine an IP 54 network hostinterface address available on CMTS 12 to receive IP 54 data packetsfrom data network 54, thereby establishing a virtual IP 54 connectionwith data network 28 via CM 16.

Returning to FIG. 13A at step 218, a first message of a first type(e.g., a DHCP 66 discover message) with a first message field for afirst connection is created on the first network device. The firstmessage is used to discover a network host interface address on thefirst network to allow a virtual connection to the third network.

At step 220, the first network device sends the first message to thesecond network device. The second network device checks the firstmessage field at step 222. If the first message field is zero, thesecond network device puts its own connection address into the firstmessage field at step 224. The second network device connection addressallows the messages from network host interfaces on the first network toreturn messages to the second network device attached to the firstnetwork device. If the first message field is non-zero, the secondnetwork device does not alter the first message field since there couldbe a relay agent attached to the first network device that may set thefirst connection address field.

At step 226, the second network device forwards the first message to aconnection address over the upstream connection to the second network.In one embodiment of the present invention, the connection address is anIP broadcast address (e.g., 255.255.255.255). However, other connectionaddresses can also be used.

The second network uses the first connection address in the firstmessage field in the first message to forward the first message to oneor more network host interfaces (e.g., IP 54 network host interfaces)available on first network at step 228. One or more network hostinterfaces available on the first network that can provide the servicesrequested in first message send a second message with a second messagetype with a second connection address in a second message field to thefirst network at step 230 in FIG. 13B. The second connection addressallows the first network device to receive data packets from the thirdnetwork via a network host interface on the first network. The firstnetwork forwards the one or more second messages on the downstreamconnection to the second network device at step 232. The second networkdevice forwards the one or more second messages to the first networkdevice at step 234. The first network device selects one of the one ormore network host interfaces on the first network using the one or moresecond messages at step 236. This allows a virtual connection to beestablished between the third network and the first network device viathe selected network host interface on the first network and the secondnetwork device.

FIGS. 14A and 14B are a flow diagram illustrating a method 240 forresolving addresses for the network host interface selected by a firstnetwork device to create a virtual connection to the third network.Turning to FIG. 14A, at step 240 one or more second messages arereceived with a second message type on the first network device from thesecond network device from the first network on a downstream connectionat step 242. The one or more second messages are offers from one or moreprotocol servers associated with one or more network host interfacesavailable on the first network to provide the first network device aconnection to the third network. The first network device selects one ofthe network host interfaces using one of the one or more second messagesat step 244. The first network device creates a third message with athird message type to accept the offered services from the selectednetwork host interface at step 246. The third message includes aconnection address for the first network in a first message field and anidentifier to identify the selected network host interface in a secondmessage field. At step 248, first network device equipment sends thethird message to the second network device.

The second network device sends the third message over the upstreamconnection to the second network at step 250. The second network usesthe first message field in the third message to forward the thirdmessage to the one or more network host interfaces available on firstnetwork at step 252.

A network host interface available on the first network identified insecond message field in the third message from the first network devicerecognizes an identifier for the selected network host interface at step254 in FIG. 14B. The selected network host interface sends a fourthmessage with a fourth message type to the first network at step 256. Thefourth message is an acknowledgment for the first network device thatthe selected network host interface received the third message. Thefourth message includes a second connection address in a third messagefield. The second connection address is a connection address for theselected network host interface. The first network stores the connectionaddress for the selected network interface from the third message in oneor more routing tables (e.g., an ARP table) on the first network at step258. The first network will forward data from the third network to thefirst network device via the second network device when it is receivedon the selected network host interface using the connection address fromthe third message field. The first network forwards the fourth messageto the second network device on the downstream connection at step 260.The second network device receives the fourth message and stores theconnection address from the third message field for the selected networkinterface in one or more routing tables on the second network device atstep 262. The connection address for the selected network interfaceallows the second network device to forward data from the third networksent by the selected network interface to the customer premiseequipment.

At step 264, the second network device forward the fourth message to thefirst network device. At step 266, the first network device establishesa virtual connection between the third network and the first networkdevice.

After step 266, the first network, the second network device and thefirst network device have the necessary connection addresses for avirtual connection that allows data to be sent from the third network toa network host interface on the first network, and from the firstnetwork over the downstream connection to the second network and then tothe first network device. In one embodiment of the present invention,method 240 accomplishes resolving network interface hosts addresses fromcustomer premise equipment with a cable modem in a data-over-cable withtelephony return without extensions to the existing DHCP protocol.

Methods 216 and 240 of the present invention are used in data-over-cablesystem 10 with telephony return with CM 16 and CPE 18. However, thepresent invention is not limited to data-over-cable system 10 withtelephony return and can be used in data-over-cable system 10 withouttelephony return by using an upstream cable channel instead of anupstream telephony channel.

FIGS. 15A and 15B are a flow diagram illustrating a method 268 foraddressing network host interfaces from CPE 18. At step 270 in FIG. 15A,CPE 18 generates a DHCPDISCOVER message broadcasts the DHCPDISCOVERmessage on its local network with the fields set as illustrated in Table6 above with addresses for CPE 18 instead of CM 16. However, more orfewer field could also be set. CM 16 receives the DHCPDISCOVER as astandard BOOTP relay agent at step 272. The DHCP DISCOVER message has aMAC 44 layer address for CPE 18 in DHCP 66 chaddr-field 132, which CM 16stores in one or more routing tables. As a BOOTP relay agent, the CM 16checks the DHCP 66 giaddr-field 130 (FIG. 6) at step 274. If DHCP 66giaddr-field 130 is set to zero, CM 16 put its IP 54 address into DHCP66 giaddr-field 130 at step 276.

If DHCP 66 giaddr-field 130 is non-zero, CM 16 does not alter DHCP 66giaddr-field 130 since there could be another BOOTP relay agent attachedto CPE 18 which may have already set DHCP 66 giaddr-field 130. Any BOOTPrelay agent attached to CPE 18 would have also have acquired its IP 54address from using a DCHP 66 discovery process (e.g., FIG. 12).

Returning to FIG. 15A, at step 278, CM 16 broadcasts the DHCPDISCOVERmessage to a broadcast address via PSTN 22 to TRAC 24. In one embodimentof the present invention, the broadcast address is an IP 54 broadcastaddress (e.g., 255.255.255.255). At step 280, one or more DHCP 66proxies 158 associated with TRAC 24, recognize the DHCPDISOVER message,and forward it to one or more DHCP 66 servers 160 associated with one ormore network host interfaces 162 available on CMTS 12. Since DHCP 66giaddr-field 130 is already non-zero, the DHCP proxies leave DHCP 66giaddr-field 130 intact. In another embodiment of the present invention,TRAC 24 includes DCHP 66 proxy 158 functionality and no separate DHCP 66proxies 158 are used.

At step 282 in FIG. 15B, the one or more DHCP servers 160 receive theDHCPDISCOVER message from one or more DHCP proxies, and generate one ormore DHCPOFFER messages to offer connection services for one or morenetwork host interfaces 162 available on CMTS 12 with the fields set asillustrated in Table 7. The one or more DHCP servers 160 send the one ormore DHCPOFFER messages to the address specified in DHCP 66 giaddr-field130 (e.g., CM 16 or a BOOTP relay agent on CPE 18), which is an IP 54address already contained in an ARP or other routing table in CMTS 12.Since CMTS 12 also functions as a relay agent for the one or more DHCPservers 160, the one or more DHCPOFFER messages are received on CMTS 12at step 284.

CMTS 12 examines DHCP 66 yiaddr-field 126 and DHCP 66 giaddr-field 130in the DHCPOFFER messages, and sends the DHCPOFFER messages down cablenetwork 14 to IP 54 address specified in the giaddr-field 130. The MAC44 address for CM 16 is obtained through a look-up of the hardwareaddress associated with DHCP 66 chaddr-field 130. If the BROADCAST bitin DHCP 66 flags-field 122 is set to one, CMTS 12 sends the DHCPOFFERmessage to a broadcast IP 54 address (e.g., 255.255.255.255), instead ofthe address specified in DHCP 66 yiaddr-field 126. CMTS 12 does notupdate its ARP or other routing tables based upon the broadcast DCHP 66yiaddr-field 126 DHCP 66 chaddr-field 132 address pair.

Returning to FIG. 15B, CM 16 receives the one or more DHCPOFFER messagesand forwards them to CPE 18 at step 286. CM 16 uses the MAC 44 addressspecified determined by DHCP 66 chaddr-field 132 look-up in its routingtables to find the address of CPE 18 even if the BROADCAST bit in DHCP66 flags-field 122 is set. At step 290, CPE 18 receives the one or moreDHCPOFFER messages from CM 16. At step 292, CPE 18 selects one of theDHCPOFFER messages to allow a virtual connection to be establishedbetween data network 28 and CPE 18. Method 266 accomplishes addressingnetwork interface hosts from CPE 18 in data-over-cable system 10 withoutextensions to the existing DHCP protocol.

FIGS. 16A and 16B are a flow diagram illustrating a method 294 forresolving network host interfaces from CPE 18. At step 296, CPE 18receives the one or more DHCPOFFER messages from one or more DHCP 66servers associated with one or more network host interface available onCMTS 12. At step 298, CPE 18 chooses one offer of services from aselected network host interface. At step 300, CPE 18 generates aDHCPREQUEST message with the fields set as illustrated in Table 8 abovewith addresses for CPE 18 instead of CM 16. However, more or fewerfields could also be set. At step 302, CPE 18 sends the DHCPREQUESTmessage to CM 16. At step 304, CM 16 forwards the message to TRAC 24 viaPSTN 22.

At step 306, a DHCP 66 layer on TRAC 24 broadcasts the DHCPREQUESTmessage on its local network leaving DHCP 66 giaddr-field 130 intactsince it already contains a non-zero value. TRAC's 24 local networkincludes connections to one or more DHCP 66 proxies. The DHCP 66 proxiesaccept DHCP 66 messages originally from CPE 18 destined for DHCP 66servers associated with network host interfaces available on CMTS 12. Inanother embodiment of the present invention, TRAC 24 provides the DHCP66 proxy functionality, and no separate DHCP 66 proxies are used.

One or more DHCP 66 proxies on TRAC's 24 local network recognize theDHCPOFFER message and forward it to one or more of the DHCP 66 serversassociated with network host interfaces (e.g., IP 54 interfaces)available on CMTS 12 at step 308 in FIG. 16B. Since DHCP 66 giaddr-field130 in the DHCPDISCOVER message sent by CPE 18 is already non-zero, theDHCP 66 proxies leave DHCP 66 giaddr-field 130 intact.

One or more DHCP 66 servers for the selected network host interfaces(e.g., IP 54 interface) available on CMTS 12 receive the DHCPOFFERmessage at step 310. A selected DHCP 66 server recognizes a DHCP 66server identifier in DHCP 66 sname-field 134 or the IP 54 address thatwas sent in the DCHPOFFER message in the DHCP 66 yiaddr-field 126 fromthe DHCPREQUST message for the selected DHCP 66 server.

The selected DHCP 66 server associated with network host interfaceselected by CPE 18 in the DHCPREQUEST message creates and sends a DCHPacknowledgment message (“DHCPACK”) to CMTS 12 at step 312 using the DHCP66 giaddr-field 130. The DHCPACK message is sent with the message fieldsset as illustrated in Table 9. However, other field settings can also beused. DHCP 66 yiaddr-field contains the IP 54 address for the selectednetwork host interface available on CMTS 12 for receiving data packetsfrom data network 28 for CPE 18.

At step 314, CMTS 12 receives the DHCPACK message. CMTS 12 examines theDHCP 66 giaddr-field 130 and looks up that IP address in its ARP tablefor an associated MAC 44 address. This is a MAC 44 address for CM 16,which sent the DHCPREQUEST message from CPE 18. CMTS 12 uses the MAC 44address associated with the DHCP 66 giaddr-field 130 and the DHCP 66yiaddr-field 126 to update its routing and ARP tables reflecting thisaddress pairing at step 316. At step 318, CMTS 12 sends the DHCPACKmessage on a downstream channel on cable network 14 to the IP 54 and MAC44 addresses, respectively (i.e., to CM 16). If the BROADCAST bit in theDHCP 66 flags-field 122 is set to one, CMTS 12 sends the DHCPACK messageto a broadcast IP 54 address (e.g., 255.255.255.255), instead of theaddress specified in the DHCP 66 yiaddr-field 126. CMTS 12 uses the MAC44 address associated with the DHCP 66 chaddr-field 130 even if theBROADCAST bit is set.

CM 16 receives the DHCPACK message. It examines the DHCP 66 yiaddr-field126 and chaddr-field 132, and updates its routing table and an ARProuting table to reflect the address pairing at step 320. At step 322,CM 16 sends the DHCPACK message to CPE 18 via CMCI 20 at IP 54 and MAC44 addresses respectively from its routing tables. If the BROADCAST bitin the DHCP 66 flags-field 122 is set to one, CM 16 sends the downstreampacket to a broadcast IP 54 address (e.g., 255.255.255.255), instead ofthe address specified in DHCP 66 yiaddr-field 126. CM 16 uses the MAC 44address specified in DHCP 66 chaddr-field 132 even if the BROADCAST bitis set to located CPE 18. At step 324, CPE 18 receives the DHCPACK fromCM 16 and has established a virtual connection to data network 28.

In the event that CPE 18 is not compatible with the configurationreceived in the DHCPACK message, CPE 18 may generate a DHCP 66 decline(“DHCPDECLINE”) message and send it to CM 16. CM 16 will transmit theDHCPDECLINE message up the PPP 50 link via PSTN 22 to TRAC 24. On seeinga DHCPDECLINE message TRAC 24 sends a unicast copy of the message toCMTS 12. CM 16 and CMTS 12 examine the DHCP 66 yiaddr-field 126 andgiaddr-field 130, and update their routing and ARP tables to flush anyinvalid pairings.

Upon completion of methods 266 and 292, CM 16 CMTS 12 have valid IP/MACaddress pairings in their routing and ARP tables. These tables store thesame set of IP 54 addresses, but does not associate them with the sameMAC 44 addresses. This is because CMTS 12 resolves all CPE 18 IP 54addresses to the MAC 44 address of a corresponding CM 16. The CMs 16, onother hand, are able to address the respective MAC 44 addresses of theirCPEs 18. This also allows DHCP 66 clients associated with CPE 18 tofunction normally since the addressing that is done in CM 16 and CMTS 12is transparent to CPE 18 hosts.

FIG. 17 is a block diagram illustrating a message flow 326 for methods268 and 294 in FIGS. 15A, 15B, and 16A and 16B. Message flow 326illustrates a message flow for methods 268 and 294, for adata-over-cable system with and without telephony return. In anotherembodiment of the present invention, CM 16 forwards requests from CPE 18via an upstream connection on cable network 14 to DHCP servers 160associated with one or more network host interfaces available on CMTS12.

Method 268 and 294 accomplishes resolving addresses for networkinterface hosts from customer premise equipment in a data-over-cablewith or without telephony return without extensions to the existing DHCPprotocol. Methods 268 and 294 of the present invention are used indata-over-cable system 10 with telephony return. However, the presentinvention is not limited to data-over-cable system 10 with telephonyreturn and can be used in data-over-cable system 10 without telephonyreturn by using an upstream cable channel instead of an upstreamtelephony channel.

Using the initialization sequences described above (FIG. 12), CM 16obtains configuration parameters at the beginning of every session ondata-over-cable system 10. CM 16 uses an IP 54 address and aconfiguration file name obtained in a DHCP 66 response message duringinitialization to establish connections to data-over-cable system 10. CM16 initiates a TFTP 64 exchange to request the configuration fileobtained in the DHCP 66 response message.

The configuration file name obtained by CM 16 includes requiredconfiguration parameters for initialization and additional parametersfor Class-of-Service and Quality-of-Service. The configurationparameters obtained in the required configuration file and additionalparameters are sent from CM 16 to CMTS 12 in a registration message.

Seamless Network Address Allocation with a Protocol Agent

DHCP 66 messaging (FIG. 12) with a DHCP 66 discover message starts withthe use of a “Martian” IP address (e.g., 0.0.0.0) as a source address(e.g., in DHCP 66 yiaddr-field 126, FIG. 6) for a network device (e.g.,CM 16) since no legitimate IP address has been assigned to the networkdevice by DHCP server 160 (FIG. 8). Since DHCP server 160 (FIG. 8) maybe at a different geographical location from other network devices inthe data-over-cable system 156, DHCP 66 messages may pass through one ormore routers on a route through data-over-cable system 156 (FIG. 8). Asis known in the art, routers translate differences between networkprotocols and route data packets to an appropriate network device on anetwork.

Routers typically use one or more types of filters to provide varyinglevels of security to a network. For example, a first type of router mayfilter all inbound messages that do not have an IP address for aspecified network such as an intranet. A second type of router mayfilter all outbound messages that are not addressed to a specific IPaddress. Other types of filters may also be used on routers. It isdesirable to use DHCP 66 messaging with routers, without having therouters filter out necessary DHCP 66 messages.

FIG. 18 is a block diagram illustrating a data-over-cable system 330 forprotocol messaging. In data-over-cable system 330, router 332 hasdifferent filters for protocol messaging. For example, a first filtermay be used in router 332 to filter out all external protocol messagesfrom data network 28 regardless of the source address to prevent a roguenetwork device from being assigned a legitimate IP address indata-over-cable system 330. A second filter in router 332 may be used tofilter protocol messages with a Martian source address since such asource address is often used to attack the data-over-cable system.However, other routers with other filters may also be used. Protocolagents 336, 338 and 340 provide network address allocation with protocolmessaging regardless of the type of filtering used in router 332.Protocol agents, 336, 338 and 340 are shown as separate entities.However, protocol agents 336, 338 and 340 may also be integral to anetwork device (e.g., as a protocol agent process) and the invention isnot limited to protocol agents as separate entities. In a preferredembodiment of the present invention, protocol agents 336, 338, and 340are DHCP 66 agents. However, other protocol agents could also be used.

FIG. 19 is a flow diagram illustrating a method 342 for protocolmessaging. Method 342 includes receiving a first message with a firstprotocol from a first network device on a first port on a protocol agentat step 344. The first port is used to send messages from the firstnetwork device via a route with one or more routers that may apply oneor more protocol filters to the first protocol. The first message issent from the protocol agent on a second port at step 346. The secondport is used to send messages via a route that does not apply protocolfilters to the first protocol. A second message is received on thesecond port on the protocol agent at step 348. The second message issent from the protocol agent to the first network device on the firstport at step 350. The first protocol server thereby avoids routefiltering of the first protocol messages by using the protocol agent tosend and receive messages on the second port.

In a preferred embodiment of the present invention, the first protocolis DHCP 66, the protocol agent is any of protocol agents 336, 338, or340 used as a DHCP 66 agent and the first network device is any of DHCPserver 160, CMTS 12, CM 16, CPE 18 or other network device.

As is known in the art, DHCP 66 uses UDP 60 as its transport protocol.For more information on UDP DHCP 66 see RFC-1541. DHCP 66 messages froma client (e.g., CM 16) to a server (e.g., DHCP server 160) are sent tothe UDP “DHCP server” port-67, and DHCP messages from a server to aclient are sent to the UDP “DHCP client” port-68. In a preferredembodiment of the present invention, first port is a UDP DHCP port(e.g., UDP DHCP client port 67 or UDP DHCP server port 68). The secondport is a UDP port other than a UDP DHCP port (e.g., other than UDPclient port-67 or UDP server port-68). Method 342 can be used with orwithout a second protocol agent on a second network device communicatingon the second port. However, the present invention is not limited tothese protocols and ports, and other protocols and ports could also beused (e.g., BOOTP protocol with TCP ports).

FIG. 20 is a flow diagram illustrating a method 352 for protocolmessaging. Method 352 includes receiving a first message on protocolagent 336 associated with DHCP server 130 with DHCP 66 protocol for anetwork device on a UDP DHCP port (e.g., UDP DHCP server port-68) atstep 354. The UDP DHCP port is used to send messages from DHCP server160 to the network device via a route with one or more routers (e.g.,332) that may apply one or more protocol filters to DCHP 66. The firstmessage is sent from protocol agent 336 to the network device on asecond UDP 60 port at step 356 (i.e., on a UDP port other than UDP DHCPserver port-68). The second UDP 60 port is used to send messages fromprotocol agent 336 on DHCP server 160 with DHCP 66 to the network deviceon a route that does not apply protocol filters to DHCP 66. A secondmessage is received on the second UDP 60 port on protocol agent 336 fromthe network device at step 358. The second message is sent from protocolagent 336 to DHCP server 160 on a UDP DHCP port at step 360 (e.g., UDPDHCP client port-67). Method 352 is described with respect to protocolagent 336 associated with DHCP server 160. However, method 352 can alsobe practiced with a protocol agent associated with CMTS 12, CM 16, CPE18, or other network devices in data-over-cable system 330 that use DHCP66 messaging.

FIG. 21 is a flow diagram illustrating a method 362 for protocolmessaging. At step 364, a first message is received on a first port on aprotocol agent with a first protocol. The first port is used to send andreceive messages via a route that may apply protocol filters to thefirst protocol. At step 366, the first message is sent from the firstprotocol agent to a second protocol agent on a second port. The secondport is used to send and receive first protocol messages for the secondprotocol agent via a route that does not apply protocol filters to thefirst protocol. At step 368, a second message is received on the firstprotocol agent from the second protocol agent on the second port. Atstep 370, the second message is sent from the first protocol agent onthe first port, thereby avoiding a route with routers that apply one ormore protocol filters to the first protocol.

In a preferred embodiment of the present invention, the first protocolis DHCP 66, the first protocol agent is a DHCP 66 protocol agent, thesecond protocol agent is a DHCP 66 agent and the first port is a UDPDHCP port, and the second port is a UDP port other than a UDP DHCP port(e.g., other than UDP DHCP port 67 or 68). However, the presentinvention is not limited to these protocols and ports, and otherprotocols and ports could also be used (e.g., BOOTP protocol with TCPports).

FIG. 22 is a flow diagram illustrating a method 372 for protocolmessaging. At step 374, a first DHCP 66 message for CM 16 is received ona first port on protocol agent 340 associated with CMTS 12. The firstport is used to send and receive messages via a route that may applyprotocol filters to DHCP 66. At step 376, the first DHCP 66 message issent from protocol agent 340 associated with CMTS 12 to protocol agent338 associated with CM 16 on a second port. The second port is used tosend and receive first protocol messages for protocol agent 338 via aroute that does not apply protocol filters to DHCP 66. At step 378, asecond DHCP 66 message is received on protocol agent 340 associated withCMTS 12 from protocol agent 338 on CM 16 on the second port. At step380, the second DHCP 66 message is sent from protocol agent 340 to CMTS12 on the first port, thereby avoiding a route with routers that applyone or more protocol filters to DHCP 66.

Method 374 is described with respect to protocol agent 340 associatedwith a CMTS 12 and protocol agent 338 associated with CM 16. However,method 362 can also be practiced with protocol agents associated withCPE 18, DHCP server 160, or other network devices in data-over-cablesystem 330.

A preferred embodiment of the present invention includes a system with aprotocol agent and a protocol agent port. The system includes a protocolagent, for sending and receiving messages for a first protocol in adata-over-cable system. The protocol agent port sends and receivesmessages for a first protocol in a data-over-cable system. The protocolagent port is used to send and receive messages via a route that doesnot apply protocol filters to the first protocol.

In a preferred embodiment of the present invention, the protocol agentis a DHCP 66 agent, and the protocol agent port is a UDP 60 port otherthan a UDP DHCP port (i.e., other than UDP DHCP ports 67 or 68).However, the present invention is not limited to these protocols andports, and other protocols and ports could also be used.

In a preferred embodiment of the present invention, the protocol agentis a software agent that implements one or more of the methods or systemdescribed herein. However, the protocol agent can also be implemented inhardware, firmware, or any combination thereof of hardware, software andfirmware

The protocol agent can be implemented in any network device indata-over-cable system 330 that uses DHCP 66 messaging (e.g., CMTS 12,CM 16, CPE 18, DHCP server 160, etc.). The protocol agent can beintegral to a DHCP 66 stack or implemented as a separate entity (e.g., aprotocol agent process).

In another embodiment of the present invention, a first message isreceived on a first port on a first network device with a firstprotocol. The first port is used to send and receive messages via aroute that may apply protocol filters to the first protocol. The firstmessage is sent from the first network device to a second protocol agenton a second port. The second port is used to send and receive firstprotocol messages for the second protocol agent via a route that doesnot apply protocol filters to the first protocol. The second networkdevice sends the message to a third network device. The second networkdevice acts as a gateway in such a scenario. As is known in the art, agateway stores and forwards data packets between dissimilar networkdevices.

The second network device adds its own network address as a gatewayaddress to the first message and puts a DHCP 66 XID from DHCP XID-field118 (FIG. 6) and/or a DHCP 66 chaddr (FIG. 6) from DHCP 66 chaddr-field132 with a DHCP 66 giaddr into an internal table. A second message isreceived on the second network device from the third network device onthe second port. The second network device looks up a DHCP 66 XID and/orDHCP 66 chaddr available in an internal table and determines that anaddress for the first network device from the internal table andforwards the second message to the first network device on the secondport. If there are no messages received for a certain period of timethen the DCHP 66 XID-field 118 and/or DHCP 66 chaddr-field 132 firstnetwork device address entry is erased.

In a preferred embodiment of the present invention, the first protocolis DHCP 66, the first port is a UDP DHCP port, and the second port is aUDP port other than a UDP DHCP port (e.g., other than UDP DHCP port 67or 68). However, the present invention is not limited to these protocolsand ports, and other protocols and ports could also be used (e.g., BOOTPprotocol with TCP ports).

In another embodiment of the present invention, the first network devicelistens for data packets and listens for messages in data packets whenthe first network device receives a DHCP 66 message destined for acertain DHCP server 160. In such an embodiment, the first network deviceputs a DHCP 66 XID from DHCP XID-field 118 (FIG. 6) and/or a DHCP 66chaddr from DHCP 66 chaddr-field 132 with a DHCP 66 giaddr into aninternal table. A second message is received on the first network devicefrom the second network device on the second port. The first networkdevice looks up DHCP 66 XID-field 118 and/or DHCP 66 chaddr-field 132the internal table and determines a DCHP 66 giaddr address from theinternal table and forwards the second message to a gateway for the DHCP66 message on the second port. If there are no messages received for acertain period of time then the DCHP 66 XID-field 118 and/or DHCP 66chaddr-field 132 first network device address entry is deleted.

A preferred embodiment of the present invention provides severaladvantages over the prior art. The protocol agent allows DCHP messagingto be used in a data-over-cable system with routers that filter certainDHCP messages, filter DCHP messages with a Martian source address orapply other DHCP filters. The protocol agent uses a designated port thatis not filtered in route to send and receive DHCP messages. ExistingDHCP servers do not have to be modified as the protocol agent handlessending and receiving messages for the DHCP servers. The protocol agentcan be used in a DHCP server, cable modem, cable modem terminationsystem, telephone remote access concentrator or other network device toprovide DHCP messaging via a route that does not apply filters to DHCPmessages.

It should be understood that the programs, processes, methods, systemsand apparatus described herein are not related or limited to anyparticular type of computer apparatus (hardware or software), unlessindicated otherwise. Various types of general purpose or specializedcomputer apparatus may be used with or perform operations in accordancewith the teachings described herein.

In view of the wide variety of embodiments to which the principles ofthe invention can be applied, it should be understood that theillustrated embodiments are exemplary only, and should not be taken aslimiting the scope of the present invention. For example, the steps ofthe flow diagrams may be taken in sequences other than those described,and more or fewer elements or components may be used in the blockdiagrams.

The claims should not be read as limited to the described order ordescribed elements unless stated to that effect. Therefore, allembodiments that come within the scope and spirit of the followingclaims and equivalents thereto are claimed as the invention.

I claim:
 1. In a data system with a plurality of network devices, amethod for protocol messaging, the method comprising the followingsteps: receiving a first message with a first protocol on a first porton a protocol agent associated with a first network device, wherein thefirst protocol is a Dynamic Host Configuration Protocol, and the firstport is used to send and receive messages for the first network devicevia a route that may apply one or more protocol filters to the firstprotocol; sending the first message from the protocol agent on a secondport, wherein the second port is used to send and receive messages forthe first network device via a route that does not apply protocolfilters to the first protocol; receiving a second message on the secondport on the protocol agent; and sending the second message from theprotocol agent to the first network device on the first port.
 2. Acomputer readable medium having stored therein instructions for causinga central processing unit to execute the method of claim
 1. 3. Themethod of claim 1 wherein the first port is a Dynamic Host ConfigurationProtocol port.
 4. The method of claim 1 wherein the second port is aport other than a Dynamic Host Configuration Protocol port.
 5. Themethod of claim 1 wherein the second port is a transmission layerprotocol port.
 6. The method of claim 5 wherein the transmission layerprotocol port is a User Datagram Protocol port.
 7. The method of claim 1wherein the step of sending the first message from the protocol agent onthe second port includes sending the first message on the second port toa second protocol agent associated with a second network device on thesecond port.
 8. The method of claim 1 wherein the second port isassociated with a separate send port for sending messages and a separatereceive port for receiving messages.
 9. The method of claim 1 whereinthe first network device is any of a protocol server, cable modem orcable modem termination system.
 10. In a data system with a plurality ofnetwork devices, a method for protocol messaging, the method comprisingthe following steps: receiving a first message with a first protocol ona first port on a first protocol agent associated with a first networkdevice, wherein the first port is used to send and receive messages viaa route that applies protocol filters to the first protocol; sending thefirst message from the first protocol agent to a second protocol agentassociated with a second network device on a second port, wherein thesecond port is used to send and receive first protocol messages via aroute that does not apply protocol filters to the second protocol;receiving a second message on the first protocol agent from the secondprotocol agent on the second port; and sending the second message fromthe first protocol agent on the first port; wherein the first protocolis a Dynamic Host Configuration Protocol, the first port is a DynamicHost Configuration Protocol port, and the second port is other than aDynamic Host Configuration Protocol port.
 11. A computer readable mediumhaving stored therein instructions for causing a central processing unitto execute the method of claim
 10. 12. The method of claim 10 whereinthe second port is a User Datagram Protocol port.
 13. The method ofclaim 10 wherein the first port is associated with a separate send portfor sending messages and a separate receive port for receiving messages.14. The method of claim 10 wherein the second port is associated with aseparate send port for sending messages and a separate receive port forreceiving messages.
 15. The method of claim 10 wherein the firstprotocol agent and second protocol agent are associated with any of aprotocol server, cable modem or cable modem termination system.
 16. Aprotocol messaging system, the system comprising: a protocol agent forsending and receiving messages for a protocol in a data system; a firstprotocol agent port, for sending and receiving messages for a protocol,wherein the first protocol agent port is used to send and receivemessages via a route that may apply one or more protocol filters to theprotocol in a data system; and a second protocol agent port, for sendingand receiving messages for a protocol, wherein the second protocol agentport is used to send and receive messages via a route that does notapply protocol filters to the protocol in a data system; wherein theprotocol is a Dynamic Host Configuration Protocol, and the secondprotocol agent port is a port other than a Dynamic Host ConfigurationProtocol port.
 17. The system of claim 16 wherein the second protocolagent port is a User Datagram Protocol port.
 18. In a data system with aplurality of network devices, a method for protocol messaging, themethod comprising the following steps: receiving a first message with aDynamic Host Configuration Protocol on a first User Datagram Protocolport on a protocol agent associated with a Dynamic Host ConfigurationProtocol server, wherein the first User Datagram Protocol port is a portused to send and receive messages for the Dynamic Host ConfigurationProtocol server via a route that applies one or more protocol filters tothe Dynamic Host Configuration Protocol; sending the first message fromthe protocol agent on a second User Datagram Protocol port, wherein thesecond User Datagram Protocol port is used to send and receive messagesfor the Dynamic Host Configuration Protocol server via a route that doesnot apply protocol filters to the Dynamic Host Configuration Protocol;receiving a second message on the second User Datagram Protocol port onthe protocol agent; and sending the second message from the protocolagent to the Dynamic Host Configuration Protocol server on the firstUser Datagram Protocol port for the Dynamic Host Configuration Protocol.19. A computer readable medium having stored therein instructions forcausing a central processing unit to execute the method of claim
 18. 20.In a data system with a plurality of network devices, a method forprotocol messaging, the method comprising the following steps: receivinga first message with a Dynamic Host Configuration Protocol on a firstUser Datagram Protocol port on a first protocol agent associated with afirst network device, wherein the first User Datagram Protocol port isused to send and receive messages via a route that applies protocolfilters to the Dynamic Host Configuration Protocol; sending the firstmessage from the first protocol agent to a second protocol agentassociated with a second network device on a second User DatagramProtocol Port, wherein the second User Datagram Protocol Port is used tosend and receive messages via a route that does not apply protocolfilters to the Dynamic Host Configuration Protocol; receiving a secondmessage on the first protocol agent from the second protocol agent onthe second User Datagram Protocol port; and sending the second messagefrom the first protocol agent to first network device on the first UserDatagram Protocol port.
 21. A computer readable medium having storedtherein instructions for causing a central processing unit to executethe method of claim
 20. 22. The method of claim 20 wherein the firstnetwork device and second network device is any of a protocol server, acable modem termination system, or a cable modem.
 23. In a data systemwith a plurality of network devices, a method for protocol messaging,the method comprising the following steps: receiving a first messagewith a first protocol on a first port on a first network device, whereinthe first port is used to send and receive messages for the firstnetwork device via a route that may apply one or more protocol filtersto the first protocol; sending the first message from the first networkdevice on a second port, wherein the second port is used to send andreceive messages for the first network device via a route that does notapply protocol filters to the first protocol; receiving the firstmessage on the second port on a second network device; adding a networkaddress for the second network device to the first message; and sendingthe first message from the second network device to a third networkdevice on the second port; wherein the first protocol is a Dynamic HostConfiguration Protocol, the first port is a Dynamic Host ConfigurationProtocol port, and the second port is other than a Dynamic HostConfiguration Protocol port.
 24. A computer readable medium havingstored therein instructions for causing a central processing unit toexecute the method of claim
 23. 25. The method of claim 23 furthercomprising: receiving a second message on the second port on the secondnetwork device from the third network device; and sending the secondmessage from the second network device to the first network device onthe second port.
 26. In a data system with a plurality of networkdevices, a method for protocol messaging, the method comprising thefollowing steps: receiving a first message with a Dynamic HostConfiguration Protocol on a Dynamic Host Configuration Protocol port ona Dynamic Host Configuration Protocol agent associated with a firstnetwork device, wherein the Dynamic Host Configuration Protocol port isused to send and receive messages via a route that applies protocolfilters to the Dynamic Host Configuration Protocol; sending the firstmessage from the Dynamic Host Configuration Protocol agent to a secondprotocol agent associated with a second network device on a second port,wherein the second port is used to send and receive messages via a routethat does not apply protocol filters to the second protocol, and whereinthe second port is a port other than a Dynamic Host ConfigurationProtocol port; receiving a second message on the Dynamic HostConfiguration Protocol agent from the second protocol agent on thesecond port; and sending the second message from the Dynamic HostConfiguration Protocol agent on the Dynamic Host Configuration Protocolport.
 27. A computer readable medium having stored therein instructionsfor causing a central processing unit to execute the method of claim 26.